One of the most common types of bone fractures in humans is a fracture of the distal radius. Inherent bony instability, soft tissue damage, and frequent associated injuries make distal radius fractures very difficult to treat. Furthermore, the functional outcome is generally directly related to residual deformity, both extra-articular alignment and intra-articular step-off. Closed methods of fixating including casting, pins and plaster, and external fixation have frequently yielded unsatisfactory results. While external fixation can restore and maintain radial length and radial shift, it cannot always restore palmar tilt or reduce articular displacement. Residual radiocarpal incongruities of more than 1 mm have been found to lead to arthritis in 91% of cases at a mean of only 6.7 years after fracture, despite good extra-articular alignment using known methods. Additionally, fixator related complications are not insignificant and the cost and duration of treatment are typically high.
Limited open reduction techniques, combined with iliac crest bone grafting and external fixation have produced good early results for simple intra-articular fractures with large fragments. Results in achieving anatomic reduction and early rehabilitation while eliminating or shortening the period of external fixation have been promising with formal open reduction and internal fixation. Furthermore, the value of immediate mobilization of the injured joints is clear, but the currently available options for internal fixation frequently fail to achieve sufficient stability in the radial bone to allow early motion with its accompanying benefits.
One device developed for internal fixation is commonly referred to as a T-plate. The T-plate was designed to buttress simple partial articular fractures of the distal radius (dorsal and volar Barton's; AO types B2 and B3) against an intact cortex and has worked well in this setting. However, for more unstable situations, particularly A3, C1, C2 & C3 by AO classification, the standard T-plate has failed with plate bending, breaking and/or screw loosening, with a consequent loss of reduction. As a result, the standard T-plate either cannot be used or must often be combined with external fixator or cast neutralization to avoid loss of reduction due to screw loosening, screw pullout, or plate bending. As a result, the benefits obtained from early mobilization cannot be achieved.
Furthermore, T-plates may not be useful in situations revolving highly comminuted fractures in which screw purchase is not available to sufficiently attach the T-plate.
U.S. Pat. No. 5,006,120 to Carter discloses one device for fixating distal radius fractures. The device includes a plate which is secured to the dorsal surface of the distal radius and a plurality of blades which are attached to the plate using threaded fasteners. Became of the separate nature of the blades and plate, movement of the blades relative to the plate and, therefore, fracture fragments, is difficult to control. In addition, the connection between the blades and plate provides an area of stress concentration which may cause catastrophic failure, such as shearing of the screw used to connect the blade and plate.
An additional disadvantage of the Carter device is that implantation requires removal of all or a portion of the cortex beneath the holes in the plate to obtain a low profile. As a result, each screw used to attach the Carter device typically does not engage more than one cortex (with a total of three cortices engaged proximal to the typical fracture pattern), thereby limiting the strength of attachment of the plate to the radius and raising the potential for screw pullout during use.
U.S. Pat. No. 5,197,966 to Sommerkamp discloses a device for fixating distal radius fractures. The device includes a plate designed for placement on the distal radiodorsal surface of the radius and includes blades, or tines, which extend from the central region of the plate for insertion into the radius. The blades are not positioned to specifically support the scaphoid and lunate fossae, and, as a result, typically do not offer the necessary level of support to the separate joint surfaces and to the subchondral bone needed to allow early mobilization.
A further disadvantage of the Sommerkamp device is that the plate will interfere with function of the first dorsal compartment tendons as well as the brachial radialis tendons. These interferences may hinder the mobilization which assists in healing.
Other attempts at internal fixation of unstable distal radius fractures include the use of small wires and mini fragment plates which have been used as internal suture to help maintain anatomic reduction. Typically, however, these methods often require an external fixator or cast for neutralization of forces across the wrist, once again eliminating the opportunity to achieve the benefits provided by early mobilization.